Research And Design Of Chipless RFID Sensor Characterizing The Dielectric Properties Of Materials

In recent years,radio frequency identification technology has gradually entered people’s lives,and people’s demand for sensors is increasing.The chip RFID sensor has high cost,while the chipless RFID sensor has the characteristics of low cost,convenient use,high measurement accuracy and high sensitivity.Therefore,this paper uses a planar resonator structure to design three chipless RFID sensors for measuring the relative dielectric constant of materials:1)In order to determine the dielectric constant and thickness of the plate material wirelessly,a chipless RFID sensor is modeled and analyzed.The sensor includes two complementary split ring resonators etched on the ground plane and two monopole antennas connected by transmission lines.The microstrip line coupled complementary split ring resonator model in the sensing area is modeled and analyzed,and the variation of the resonant frequency of the two resonators with the characteristics of the measured material is studied.Through simulation and data analysis,when the thickness of the measured material is in the range of 2.5 mm ～ 4 mm,the linear relationship between the transmission zero between the two antennas and the relative dielectric constant and thickness of the measured material is determined.The analysis results show that the relative dielectric constant and thickness of the measured material can be characterized theoretically by the RCS transmission zero of the sensor.The relative error of the relative dielectric constant is within 5 %,and the relative error of the thickness is within 10 %.2)In order to improve the sensitivity of the sensor to measure the dielectric constant,based on the structure of the microstrip line coupled complementary split ring resonator,a method to improve the sensitivity of the sensor is studied and proposed: reducing the relative dielectric constant of the dielectric substrate used in the sensor and reducing the microstrip line width of the excitation resonator.Based on the model of microstrip line coupled resonator,a chipless RFID sensor with high sensitivity is designed.The sensor includes two circular monopole antennas connected by transmission lines and a floor.Two complementary split-ring resonators are etched on the floor.Two cylindrical holes are dug on the dielectric substrate directly above the resonator,and fine wires are connected.Through simulation and data analysis,when the thickness of the measured material is in the range of 2 mm ～ 4 mm,the linear relationship between the two transmission zeros of the sensor and the relative dielectric constant and thickness of the measured material can be established,and the sensitivity of the sensor is increased by 10.8 %.3)In order to improve the ability of the sensor to be identified in the measured environment,based on the microstrip line coupled complementary split ring resonator structure,the sensor structure is improved to achieve the response characteristics with transmission poles.The specific improvement measure: disconnect the microstrip line of the excitation resonator.Based on the model of microstrip line coupled resonator,a chipless RFID sensor with transmission pole characteristics is designed.The sensor includes two circular monopole antennas connected by transmission lines and a floor.A complementary split ring resonator is etched on the floor and the microstrip line that excites the resonator is disconnected.Through simulation and data analysis,the relationship between the transmission pole response of the sensor and the relative dielectric constant of the measured material is established.The measured data show that the relative dielectric constant error of the sensor is within 5 %.